Establishing a Voice Call

1. A method comprising: receiving, by a user equipment (UE) that is able to use a plurality of different wireless access technologies, a request to establish a voice call; storing a device configuration parameter in a storage medium of the UE, the device configuration parameter dynamically configured by a mobile communications network; setting a value of the device configuration parameter to one of a first value and a second value responsive to a message received from the mobile communications network, wherein the device configuration parameter when set to the first value indicates that voice over a packet-switched domain is supported by the first wireless access technology, and the device configuration parameter when set to the second value indicates that voice over the packet-switched domain is not supported by the first wireless access technology; and in response to the request to establish the voice call: accessing, by the UE, the device configuration parameter stored in the UE, determining, by the UE based on the device configuration parameter accessed in response to the request to establish the voice call, whether voice over the packet-switched domain is supported by the first wireless access technology, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, attempting to establish, by the UE, the voice call over a second wireless access technology of the different wireless access technologies.

2. The method of claim 1 , wherein the second wireless access technology performs a voice call in a circuit-switched domain.

3. The method of claim 1 , wherein the first wireless access technology is a Long-Term Evolution (LTE) wireless access technology.

4. The method of claim 1 , wherein receiving the request to establish the voice call comprises receiving a request to establish an emergency voice call responsive to a user selection at the UE.

5. The method of claim 1 , further comprising, in response to the request initiated by a user at the UE: responsive to determining that voice over the packet-switched domain is supported by the first wireless access technology, attempting to establish, by the UE, the voice call over the first wireless access technology.

6. The method of claim 1 , wherein the device configuration parameter is stored in a Subscriber Identity Module (SIM) of the UE.

7. The method of claim 6 , wherein the device configuration parameter is statically configured in the UE.

8. The method of claim 1 , wherein the determining and the attempting to establish are performed in response to the UE being out of wireless coverage of a home network of the UE.

9. A user equipment (UE) comprising: a storage medium to store a device configuration parameter that is dynamically configurable by a mobile communications network; at least one wireless interface to communicate with the mobile communications network according to one or more of a plurality of different wireless access technologies; and at least one processor configured to: set a value of the device configuration parameter to one of a first value and a second value responsive to a message received from the mobile communications network, wherein the device configuration parameter when set to the first value indicates that voice over a packet-switched domain is supported by a first wireless access technology of the different wireless access technologies, and the device configuration parameter when set to the second value indicates that voice over the packet-switched domain is not supported by the first wireless access technology; receive a request to establish an outgoing voice call from the UE; and in response to the request to establish the outgoing voice call from the UE: access the device configuration parameter stored in the UE, determine, based on the device configuration parameter accessed in response to the request to establish the outgoing voice call, whether voice over the packet-switched domain is supported by the first wireless access technology, and responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology is not supported, initiate establishing the outgoing voice call over a second wireless access technology of the different wireless access technologies.

10. The UE of claim 9 , wherein the determining of whether voice over the packet-switched domain is supported by the first wireless access technology comprises determining whether voice over Long-Term Evolution (LTE) is supported.

11. The UE of claim 9 , wherein the initiating the establishing of the outgoing voice call over the second wireless access technology comprises initiating the establishing of the outgoing voice call in a circuit-switched domain.

12. The UE of claim 9 , wherein the at least one processor is configured to further, in response to the request: responsive to determining that voice over the packet-switched domain is supported by the first wireless access technology, initiate establishing the outgoing voice call over the first wireless access technology.

13. The UE of claim 12 , wherein the initiating the establishing of the outgoing voice call over the first wireless access technology comprises initiating the establishing of the outgoing voice call in the packet-switched domain.

14. An article comprising at least one non-transitory machine-readable storage medium storing instructions that upon execution cause a user equipment (UE) to: store, in a storage medium of the UE, a device configuration parameter that is dynamically configurable by a mobile communications network; set a value of the device configuration parameter to one of a first value and a second value responsive to a message received from the mobile communications network, wherein the device configuration parameter when set to the first value indicates that voice over a packet-switched domain is supported by a first wireless access technology of different wireless access technologies, and the device configuration parameter when set to the second value indicates that voice over the packet-switched domain is not supported by the first wireless access technology; receive a request to establish an outgoing voice call; and in response to the request to establish the outgoing voice call: access the device configuration parameter stored in the UE, determine, based on the device configuration parameter accessed in response to the request to establish the outgoing voice call, whether voice over the packet-switched domain is supported by the first wireless access technology, responsive to determining that voice over the packet-switched domain is not supported by the first wireless access technology, initiate establishing the outgoing voice call over a second wireless access technology that performs voice communication in a circuit-switched domain, and responsive to determining that voice over the packet-switched domain is supported by the first wireless access technology, initiate establishing the outgoing voice call over the first wireless access technology.

15. The article of claim 14 , wherein the request to establish the outgoing voice call is a request to establish an emergency voice call responsive to a user dialing an emergency number.

16. The article of claim 14 , wherein the outgoing voice call over the second wireless access technology is in the circuit-switched domain, and wherein the outgoing voice call over the first wireless access technology is in the packet-switched domain.